Steam turbine lubricants



Patented Apr. 29, 1952 STEAM TURBINE LUBRICANTS Harry W. Rude], Roselle Park, and Jones I. Wasson, Union, N. .L,

assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application January 25, 1946, Serial No. 643,456

Claims. 1

The present invention relates to the field of lubricants and especially to lubricating oils useful for the lubrication of steam turbines.

Steam turbines are employed as the prime movers in many installations, such as alternatingcurrent generators, turbo-compressors, blowers and marine propellers, and, by means of reducing gears, to furnish power for reciprocating air compressors, rolling mills and other classes of flowsteam machinery, where a regular and abundant flow of power is required. During the normal op eration of a steam turbine there is a considerable amount of steam condensation throughout various parts of the turbine. There is also some leakage of cooling water and water from other sources, all of which eventually comes in contact with the oil used for lubrication purposes in connection with the turbine. The presence of water in the oil gives rise to some difficulty. The turbine journal revolving at possibly 3600 R. P. M. acts as a homogenizer of oil and water, resulting in an oil and water emulsion. Settling tanks are provided to permit the emulsion to break. However, where the emulsion does not break fast enough it will be pumped into the lubrication system where it may clog small orifices in the system. Also, the presence of even small amounts of water tends to cause corrosion of parts of the turbine, particularly the intricate parts of the valve and governor mechanism. In the case of marine turbines Where sea Water is present and salt permeates the atmosphere, these corrosion problems are even more pronounced. These problems have been recognized and attempts made to overcome them by the use of materials in the nature of corrosion inhibitors in the oil. Such attempts have not been entirely successful due to the fact that the inhibitors used have usually been of the soap type which increase emulsion formation.

The principal object of the present invention is the provision of a novel corrosion inhibitor for oils. Another object is a lubricating oil containing an oxidation inhibitor which does not promote emulsification of oil and Water. These and other objects will be apparent to those skilled in the lubricant art upon reading the following description.

It has now been found that certain ether or thio ether derivatives of tetraand hexa-hydrophthalic acids, tetraand hexa-hydrophthalic anhydrides or a mono-ester of tetraand hexahydrophthalic acids and alkyl substitutedderivatives thereof are excellent corrosion inhibitors in lubricating oils, particularly where such oils may come in contact with water. The most probable formulas for representing the acid and ester forms of the corrosion inhibitors of the present invention are:

substituted tetra-liydroph thalic substituted hexa-hydrophthalic acid or mono-ester acid or mono-ester wherein R1, R2, R3, R4, R5, R5, and R7 are either hydrogen or an alkyl radical such as methyl, ethyl, propyl, etc.; R3 and R9 are alkyl radicals of 4 to 20 carbon atoms, cycloalkyl radicals such acyclopentyl or cyclohexyl, aryl radicals such phenyl or naphthyL'aralkyl radicals like benzyl or alkaryl radicals such as tolyl, R10 is either hydrogen or an alkyl radical of from 4-20 carbon atoms; X is an element selected from the righthand column of group VI of the periodic table, which includes oxygen, sulfur, selenium and tellurium. A representative formula for derivatives wherein R1, R2, R3, R4, R5, R6, R7, R8 and R9, as Well asX, are the same as described above in connection with the tetraand hexa-hydro acids and esters.

,A convenient method of making the corrosion inhibitors of the present invention employs a toluene, cooling must be employed to maintain the temperature below the boiling point of the solvent. With isoprene and maleic anhydride as the reactants, the Diels-Alder condensationforming fi-methyl, A tetra-hydrophthalic anhydride, or 5-methyl i-cyclohexene, 1,2-dicarboxylic acid anhydride, is illustrated by the fol lowing equation: 7

When reacted with an aliphatic mercaptan such as pentadecyl mercaptan in the presence of a Friedel-Crafts type catalyst such as BPS, the tetra-hydrophthalic anhydride yields the 4- pentadecyl thio ether of B-methyl hexa-hydrophthalic anhydride by the addition of the mercaptan at the double bond. A typical example of a hydrocarbon derivative of chlor-maleic anhydride is alphachlor-beta-methyl maleic anhydride.

Following the Diels-Alder reaction, after removal of the solvent, the condensation product is reacted with an alkali metal alcoholate or mercaptide (or a corresponding seleno or telluro compound) in the presence of a solvent such as methanol, isopropyl alcohol, etc. The chloro cyclo dibasic acid anhydride is first dissolved in a solvent such as methyl alcohol and an alcoholic solution of the alkali metal compound such as a mercaptide is added, the mixture then refluxed for 15 minutes to 1 hour, preferably about 30 minutes, resulting in the replacement of the halogen atom by the organic radical of the alkali metal compound and the formation of alkali metal halides. If the anhydride form of the product is desired, the reaction product is filtered to remove the alkali metal halide and the solvent is recovered by distillation. To obtain the acid form, the product is hydrolyzed with acidified water, precipitating the free dicarboxylic acid which is recovered by filtration and washed to remove the alkali metal halide. Both the anhydride and the acid forms of these products provide excellent corrosion inhibitors for turbine oils.

The compounds of the foregoing reaction may be reacted with additional alcohol or mercaptans to obtain further substituted derivatives which are also excellent corrosion inhibitors. Where 1 mol of alcohol or mercaptan is used per mol of cyclo dibasic acid anhydride, the alcohol or mercaptan adds across the double bond giving a substituted cyclohexane dicarboxylic acid anhydride. Two molecules of the alcohol or mercaptan produce the mono-ester of the substituted cyclohexane dicarboxylic acid. Alcohols and mercaptans as employed in this reaction, as well as the alcoholates and mercaptides of the previously described reaction, may contain from 4-20 carbon atoms, although it is preferred to use compounds having from 12-16 carbon atoms in the molecule. This reaction is carried out by dissolving the anhydride from the previous reaction in the alcohol or mercaptan and bubbling BF3 into the solution, 150 C. for from 15 minutes to 1 hour, about 30 minutes.

Although use in' turbine oils has been cmphasized in describing the present invention, the principles thereof are also applicable to other preferably heated to lubricating oils, such as gear oils, motor oils, etc. where emulsion and corrosion problems due to water are encountered. The corrosion inhibitors of the present invention may be used in amounts ranging from 0.01 to 0.5% based upon the quantity or" oil, preferably ODS-0.1%, in highly refined lubricating oils ranging in viscosity from 35 to S. S. U. at 210 F. V. I. improvers, pour depressors and oiliness agents may be used in conjunction with the corrosion inhibitors of the present invention if desired.

Having described the invention generally, the following examples will serve to illustrate specific embodiments of the invention.

Example 1 132 parts by weight of chlor-maleio anhydride was dissolved in 200 parts of toluene, the solution put in a reactor equipped with a stirrer and the reactor placed in an alcoholic Dry Ice bath. 68 parts by weight of isoprene was then added to the reactor accompanied by continuous agitation 1n order to maintain the temperature within the reactor below the boiling point of isoprene. After the isoprene was added the mixture was stirred for 10 minutes to insure completion of the reaction. The toluene was then recovered by distillation. 200 parts by weight of l-chloro, E-methyl tetra-hydrophthalic acid anhydride was recovered. This chlor-anhydride was dissolved in 200 parts by weight of methanol and added to a reactor along with 266 parts by weight of sodium pentadecyl mercaptide in 500 parts of methanol, equipped with a reflux condenser. The mixture was refluxed for 30 minutes at 66 C. After cooling, the reaction mass was filtered to remove sodium chloride and then distilled to recover methyl alcohol. 382 parts by weight of l-pentadecyl thio ether of 5-methyl tera-hydrophthalic acid anhydride was recovered after distillation. The product was a white wax-like, low-melting solid.

Example 2 191 parts by weight of the product from Example 1 was mixed with 122 parts by weight of pentadecyl mercaptan, BFs bubbled in for about minute and then the product heated in a reactor to 150 C. for one hour. The material was washed with water to remove residual catalyst and dried. The product consisted of 313 parts of substituted phthalic acid having the following chemical composition:

wherein R1, R2, R3, R4, R5, R6, and R7 are either hydrogen or an alkyl radical such as methyl, ethyl, propyl, etc.; Re and R9 are alkyl radicals of 4 to 20 carbon atoms, cycloalkyl radicals such as cyclopentyl or cyclohexyl, aryl radicals such as phenyl or naphthyl, aralkyl radicals like benzyl or alkaryl radicals such as tolyl; X is an element selected from the righthand column of group VI of the periodic table, which includes oxygen, sulfur, selenium and tellurium.

The corrosion inhibiting properties of the free acids produced in Examples 1 and 2 are illustrated by the following data on mineral oil blends in contact with polished steel, in the presence of synthetic sea Water (AS'IM D-665-42T rust test) This test is conducted by suspending the polished steel specimen in 300 mls. of the test oil, plus 30 mls. of synthetic sea water at 140 F. for 48 hours, noting the extent of corrosion atthat time.

Extent of Busting in ASILI D-6G5-42 'lest (After 48 Hours) Blend Lubricating Oil (Turbine Oil) Lubricating Oil 0.1% 4,pentadecyl thio,

S-methyl hexa-hydrophthalic acid Lubricating Oil 0.1% Lpentadecyl thio, -methyl tctra-hydrophthalic acid (from Example 1) Lubricating Oil 0.1% 1,4 di(pentadecyl thio), fi-methyl hexa-hydropthalic acid (from Example 2) Heavy.

Medium.

Nil.

Nil.

The advantage of substituting the alkyl thio group in a position alpha to the carboxyllc acid is clearly evidenced by the above data.

What is claimed is:

1. A lubricating composition consisting essentially of mineral base lubricating oil containing 0.01 to 0.5% by Weight, of a compound selected from the class which consists of thioether substituted tetrahydrophthalic and hexahydrophthalic acids, and the anhydrides, and monoesters thereof having at least one thioether substitution including one organic radical attached in alpha position to an acyl radical through a thioether linkage.

2. A lubricating composition consisting essen tially of a mineral oil and Mil-0.5% of a compound having the general formula where R1, R2, R3, R4, R5, R6 and R7 are substituents selected from the group consisting of hydrogen and alkyl radicals, R8 and R9 are hydrocarbon radicals selected from the group consisting of alkyl, cycloalkyl, aryl, aralkyl and alkaryl radicals, R10 is a substituent selected from the group consisting of hydrogen and alkyl radicals of 4-20 carbon atonis, cycloalkyl, aryl, aralkyl and alkaryl radicals; X is an element selected from the group consisting of oxygen and sulfur.

4. A lubricating composition consisting essentially of a mineral oil and 0.01-0.5% of a compound having the general formula where R1, R2, R3, stituents tially of a mineral oil and 0.05-0.1% of 1-pentadecyl thio, 5-methyl tetrahydrophthalic acid.

6. A lubricating composition consisting essentially of a mineral oil and 0.050.1% of 1,4-di- (pentadecyl thio) 5-methyl hexahydrophthalic acid.

7. A'lubricating composition consisting essentially of a mineral oil and 0.05-O.1% of monopentadecyl thio ester of 1,4(dipentadecyl thio) S-methyl hexa-hydrophthalic acid.

8. A lubricating composition consisting essentially of a mineral oil and about 0.1% of 1,- pentadecyl thio, 5-methyl tetrahydrophthalic acid.

9. A lubricating composition consisting essentially of a mineral oil and about 0.1% of 1,4- di(pentadecyl thio) 5-methyl hexa-hydrophthalic acid.

10. A lubricating composition consisting essentially of a mineral oil and about 0.1% of monopentadecyl thio ester of 1,4(dipentadecyl thio) fi-methyl hexa-hydrophthalic acid.

HARRY W. RUDEL. JONES I. WASSON.

REFERENCES CITED The following references are of record in the file of this patent:

OTHER REFERENCES Chemical Abstracts, pg. 3647, vol. 38, 1944. 

1. A LUBRICTING COMPOSITION CONSISTING ESSENTIALLY OF MINERAL BASE LUBRICATING OIL CONTAINING 0.01 TO 0.5% BY WEIGHT, OF A COMPOUND SELECTED FROM THE CLASS WHICH CONSISTS OF THIOETHER SUBSTITUTED TETRAHYDROPHTHALIC AND HEXAHYDROPHTHALIC ACIDS, AND THE ANHYDRIDES, AND MONOESTERS THEREOF HAVING AT LEAST ONE THIOETHER SUBSTITUTION INCLUDING ONE ORGANIC RADICAL ATTACHED IN ALPHA POSITION TO AN ACYL RADICAL THROUGH A THIOETHER LINKAGE. 